Jon Crowcroft

Bio: Jon Crowcroft is an academic researcher from University of Cambridge. The author has contributed to research in topics: The Internet & Multicast. The author has an hindex of 87, co-authored 672 publications receiving 38848 citations. Previous affiliations of Jon Crowcroft include Memorial University of Newfoundland & Information Technology University.

Containment: From context awareness to contextual effects awareness

Abstract: Context plays a key role, as recongnized by a wide body of research, in application and entity adaptation in the ubiquitous computing world characterized by extensive platform heterogenity and environment dynamicity and unpredictability. Implicit in the notion of context, as used by context-aware applications, is the actual effects, including constraints, context has on target entities. We believe that making a step further from explicit reasoning about context to explicit reasoning about its implicit effects will facilitate more effective and flexible adaptation. In this work we present an approach to modeling the world based on natural notions of container and containment and show how it enables explicit reasoning about and acting upon context-implied effects on target entities, data objects in particular. We also outline a practical use of the model through its application in a system for autonomic context-aware infromation security and privacy protection.

A generic Management Information Base browser

Abstract: A Management Information Base browser is a very important application in any management environment as it enables a human manager to browse through the Management Information Tree of a remote managed system, looking at and possibly modifying management information. Such an application can be designed in a generic way, without prior knowledge of the managed object classes present in a managed system. This results in a tool that can cope with different versions of standard MIBs, proprietary extensions or even newly introduced ones. The issues behind the concepts and the design of the generic browser are presented in this paper; special attention is given to the issue of coping with changes in the remote MIB in a generic fashion. Keyword Codes: C.2.3; C.2.4

Exploiting contextual handover information for versatile services in NGN environments

Abstract: Users in ubiquitous and pervasive computing environments will be much more empowered in ways to access and to control their navigation. Handover, the vital event in which a user changes the attachment point in a next generation network (NGN), is an important occasion and the conditions and environment in which it is executed can offer relevant information for businesses. This paper describes the capabilities of a platform which intends to exploit contextual handover information offering a rich environment that can be used by access and content providers for building innovative context-aware multi-provided services. Based on ontologies, the technique not only eases the building of versatile services but also provides a comprehensive source of information both for enriching user navigation in the network as well as for the improvement of the provider's relationship with their customers.

TCP-XM: unicast-enabled reliable multicast

Abstract: In recent years, much work has been done on attempting to scale multicast data transmission to hundreds or thousands of receivers. There are, however, many situations where an application might involve transmission to just ten or twenty sites. Using multicast for this type of application can provide significant benefits including reduced load on the transmitter an overall reduction in network traffic, and consequently shorter data transfer times. In this project, we are investigating how partial or incomplete multicast can be exploited alongside reliable unicast to improve both speed and efficiency of data transfers while maintaining reliability. The approach taken is to combine unicast with multicast by modifying TCP to support multicast transfers, and run this modified TCP engine over UDP as a userspace transport protocol. We describe the work to date on the design and implementation, and provide experimental results from our tests across both local and wide area networks.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Community detection in graphs

Abstract: The modern science of networks has brought significant advances to our understanding of complex systems. One of the most relevant features of graphs representing real systems is community structure, or clustering, i. e. the organization of vertices in clusters, with many edges joining vertices of the same cluster and comparatively few edges joining vertices of different clusters. Such clusters, or communities, can be considered as fairly independent compartments of a graph, playing a similar role like, e. g., the tissues or the organs in the human body. Detecting communities is of great importance in sociology, biology and computer science, disciplines where systems are often represented as graphs. This problem is very hard and not yet satisfactorily solved, despite the huge effort of a large interdisciplinary community of scientists working on it over the past few years. We will attempt a thorough exposition of the topic, from the definition of the main elements of the problem, to the presentation of most methods developed, with a special focus on techniques designed by statistical physicists, from the discussion of crucial issues like the significance of clustering and how methods should be tested and compared against each other, to the description of applications to real networks.